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Lantronix
SM24TBT2DPA and SM24TBT2DPB Web User Guide
2-4.3 Relay
A DHCP relay agent is used to forward and to transfer DHCP messages between clients and the server
when they are not in the same subnet domain. It stores the incoming interface IP address in the GIADDR
field of the DHCP packet. The DHCP server can use the value of GIADDR field to determine the assigned
subnet. For such condition, please make sure the switch configuration of VLAN interface IP address and
PVID (Port VLAN ID) correctly.
Web Interface
To configure DHCP Relay in the web interface:
1. Click Configuration, DHCP, Relay.
2. Specify the Relay Mode, Relay server, Relay Information Mode, Relay Information police.
3. Click Apply.
Figure 2-4.3: DHCP Relay Configuration page
Parameter descriptions:
Relay Mode:
Indicates the DHCP relay mode operation. Possible modes are:
Enabled
: Enable DHCP relay mode operation. When DHCP relay mode operation is enabled, the agent
forwards and transfers DHCP messages between the clients and the server when they are not in the
same subnet domain. And the DHCP broadcast message won't be flooded for security considerations.
Disabled
: Disable DHCP relay mode operation.
Relay Server:
Indicates the DHCP relay server IP address.
Relay Information Mode:
Indicates the DHCP relay information mode option operation. The option 82
circuit ID format as "[vlan_id][module_id][port_no]". The first four characters represent the VLAN ID, the
fifth and sixth characters are the module ID (in standalone device it always equals 0), and the last two
characters are the port number. For example, "00030108" means the DHCP message was received from
VLAN ID 3, switch ID 1, port No 8. And the option 82 remote ID value is equal the switch MAC address.
Possible modes are:
Enabled
: Enable DHCP relay information mode operation. When DHCP relay information mode
operation is enabled, the agent inserts specific information (option 82) into a DHCP message when
forwarding to DHCP server and removes it from a DHCP message when transferring to DHCP client. It
only works when DHCP relay operation mode is enabled.
Disabled
: Disable DHCP relay information mode operation.